diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
index e4ff3ca676cf..584a930472f2 100644
--- a/lib/matplotlib/font_manager.py
+++ b/lib/matplotlib/font_manager.py
@@ -862,7 +862,7 @@ def set_stretch(self, stretch):
         'ultra-expanded', or a numeric value in the range 0-1000.
         """
         if stretch is None:
-            stretch = rcParams['font.weight']
+            stretch = rcParams['font.stretch']
         try:
             stretch = int(stretch)
             if stretch < 0 or stretch > 1000: